1. Field of the Invention
The present invention relates to an image reading apparatus for reading an image of an original, such as an image scanner, a multifunction machine (multifunction peripheral), a copying machine, or a facsimile apparatus.
2. Description of the Related Art
An image reading apparatus of a flatbed type is provided with an original glass table, a carriage whose part slides on a guide rail while moving substantially in parallel to the original glass table, and an image reading sensor mounted on the carriage, for reading an image of an original placed on the original glass table as the carriage is moved. A unit for moving the carriage has been known as being configured to transmit drive force of a drive motor housed inside of the apparatus via a plurality of gears and pulleys, a drive wire, and the like. (See Japanese Patent Application Laid-open No. 2002-44385.)
There has been known a scanning type in which a guide rail and a belt are eliminated, and further, a component part having an image reading sensor mounted thereon runs by itself on a rack molded with plastic in place of a guide rail so as to reduce a cost. (See Japanese Patent Application Laid-open No. 2004-54283.)
An image reading apparatus has recently required a high reading accuracy for the purpose of a high resolution, and further, it has required miniaturization and thinness from the viewpoint of usability. In order to read an image with a high accuracy, feedback control is carried out such that an encoder is employed to monitor the rotation of a DC motor for driving a carriage having an original reading sensor mounted thereon. However, for the purpose of the implementation of the feedback control, a board or the like having the encoder mounted thereon is fixed to the DC motor, thereby enlarging a space in a thickness direction of the apparatus in, for example, a conventional product. Moreover, a drive unit housed inside of the image reading apparatus is disposed at a lower portion of the carriage having the image reading sensor mounted thereon or on the lower portion and a side of the carriage, and therefore, the size, in particular, the thickness of a scanner unit becomes great. As a consequence, the thickness of the apparatus also becomes great.